#1
I can play C#m and F on barre chords. I hold my fingers tightly and all of the notes are played. But When positioning only fore-finger in a barre chord position on any fret, String G and B don't sound well. Those two notes doesn't played.
Any tips how to make it better?
#2
Make sure that your index finger is as close as possible to the fret itself. Imagine the fret being a wall that extends perpendicularly from your neck and try to have your finger right next to it. This helped me a lot in the beginning, now it's just easy and second nature. By the way, the action on your guitar matters too. If your action is too high, it will make barre chords more difficult.

Good Luck!!
Light is faster than sound. That is why some people appear bright until you hear them speak.

Quote by Scott3229
if i wanted to get brain washed and then throw all my money away, id go to church


"I see, you've been blinded by what you believe" Sully Erna
#3
^--- is correct about your action. the lower your action and the lighter your strings, the easier barre chords are going to be. i wouldn't really recommend going with a lighter string gauge just to facilitate barre chords though. the best thing you can do is just keep on practicing. your hand, fingers, and arm will get stronger through practice and you'll be able to play those barre chords cleanly without trouble after a while.